The Souls That Bind Us
by SoulFire820
Summary: Two humans that are siblings end up in the underground. One is getting close with a punny skeleton and the other is slowly being possessed by a demon child. Will they be able to correct the timeline and free everyone from their prison? Or will they be trapped in a never ending battle forever?
1. Dawning

**Hello everyone my name is Camellia20 and this is my first story on this site. I fuckin' love Undertale! I first heard it referenced in the game Yandere Simulator, but didn't know what it was. So when I looked into it and found out it was a game I had watched Jacksepticeye play it. Best thing I ever did. This game is absolutely amazing! The characters, the humor, the music, and the story is all phenomenal. I strongly advice you to play the game or at least watch someone else do it. Then again you probably wouldn't have clicked on this story if you hadn't. Either way this was just an idea I had. I hope you enjoy it and I will try and update as much as I can. Now if you'll excuse me I'm gonna head to Grillby's. Take care my Little Souls.**

"Frisk? Frisk!" a female voice desperately called out.

Running through the forest a girl with long black hair tied up in a ponytail wondered where her little sibling wandered off to. Frisk had ran out of their house with tears threatening to fall after hearing tragic news. The older sibling had let them run off to give them space, but when they failed to return home the girl grew worried. Knowing that Frisk sometimes strolled through the forest whenever they were upset the girl began her search there. But she didn't know what direction to they went in. What if she was going the opposite way?

Growing frustrated the girl continued to stumble through the think bramble that tried to block her path. The smell of embers burned her nose as the sound of crickets chirping and a owl hooting filled her ears. Why hadn't she brought a flashlight? It would have made her search a lot easier.

Calling her siblings name the girl noticed she was getting closer to the mountain that loomed before the town. It was known as Mount Ebott and had quite a famous history. It was also the doorway to the underground world. Knowing that's where monsters were banished the dark haired girl grew worried that's where Frisk ran off to. Seeing how they were nowhere to be found in the forest she decided to give the mountain a try. Even if they weren't up there maybe she could at least spot them from higher ground.

Ignoring her legs screaming at her for a rest she began her journey up the mountain. She couldn't rest. Not until she knew her sibling was safe. She couldn't lose the only family she had left.

Panting as she reached the top she grew disappointed as her search didn't seem to come to an end. Where were they? Noticing something shining near the entrance of the underground she moved closer only to have her eyes widen in distress. Hanging from a small branch near the edge of the opening was a golden heart shaped locket. It had belonged to Frisk. Somewhat relieved that she was heading in the right direction the girl was also concerned that her younger sibling was trapped in the same world where monsters lived.

Even though it appeared to be a long way down the girl decided to risk going down anyway. Grabbing the locket and putting it around her neck she began to carefully climb inside. Though that didn't work out so well. Being the somewhat clumsy girl that she is she wasn't overly surprised when she slipped and started falling into the dark abyss below. A weird sensation flowed through her body making her pretty sure that she had just passed through the barrier that kept monsters imprisoned under the mountain. That meant that Frisk and her were trapped too.

Letting out a scream as she fell the girl groaned in pain when she finally hit the bottom. It didn't hurt as much as she thought it would. She was grateful for landing on what felt like a bed of flowers, but the shock of falling down such a long distance was enough to cause her to black out. The last thing she saw before her eyes fluttered shut was a golden flower with a face staring back at her.

 _"Frisk, where are you…?"_

 _"Hey get back here!" a girl with indigo colored eyes laughed as she chased a younger person with short brown hair and a striped shirt around their backyard._

 _The gender neutral child silently giggled in response as they tried to prevent themselves from being tagged. They played together while their parents were out running a few errands. The phone ringing from inside had put their little game on hold as the older girl went to answer it._

 _"Hello?" she responded as soon as she answered._

 _A man's voice she didn't recognize began speaking to her in a sad apologetic way. Her eyes grew wide hearing the words coming out of his mouth. Oh no. Oh please no. She didn't even give the man a chance to finish speaking before the phone dropped from her hand in complete shock._

 _"Hello? Hello ma'am are you there?" the man's voice called out wondering if they got cut off or something._

 _Instead of picking the phone back up the girl slowly backed up until she hit a wall. Once she did she slowly slid down it; bringing her knees to her chest. Her whole body began to tremble as tears started to spill from her eyes. Not hearing small footsteps enter the room the small child grew concerned seeing their older sister crying. The girl slowly lifted her head when she felt a small hand being placed on her knee._

 _"Sis?" the brown haired child questioned, using their hands to speak since they couldn't do it verbally. "What's wrong?"_

 _Taking a shaky breath the black haired girl wasn't sure if she would be able to tell them the tragic news she just received._

 _"Frisk.." she began, but stopped and bit her lip._

 _She had to tell them. There was no way she could hide it. Taking another deep breath to try and calm her nerves for a brief moment she sadly spoke the next sentence that broke her siblings heart._

 _"Mom and Dad aren't coming home.."_

Sitting up quickly the girl breathed heavily as the dream she had replayed the horrific events that just took place. Wiping the sweat forming on her forehead she grew confused seeing that she had been laying on an actual bed instead of one made of flowers. She would have prayed that it had all been a terrible dream, but knew it was real when she didn't recognize her surroundings.

Pulling her phone out of her jean shorts pocket her eyes squinted at the bright light it gave off as it lit up the dark room. She checked the time to see that it was seven in the morning. She had been asleep for nine hours. Sighing she pocketed her phone before standing up to look around the room. Turning on the lamp she saw that it appeared to be a children's bedroom, and there was evidence of children living in here before, with shoes of various sizes found inside a box. A drawing of a golden flower was above it and looked to have been made a long time ago. It reminded her of the strange flower that she saw before she passed out. A dusty photo frame sat on top of a dresser and was strangely empty. Inside the wardrobe was a bunch of striped shirts that reminded her of her siblings clothing. Speaking of Frisk she had to find them.

Making her way to the door, she poked her head out to see no one in the hallway. Whoever brought her here must have been friendly if they gave her a safe warm place to sleep in. Walking out she made her way down the hall and past some stairs to the living room. It looked rather cozy with a fireplace that crackled with bright orange flames and a big comfy chair. There was also a bookshelf and a table with three chairs.

The sound of soft humming got the girl's attention and she slowly made her way to the kitchen to finally see who or what lived here. Poking her head around the corner she saw a large goat woman with white fur in a long purple robe standing with her back facing her. The woman hummed a sweet melody as she cleaned a plate with pie crumbs on it. Her phone hadn't been placed in her pocket properly and ended up slipping out, falling to the floor. Luckily it didn't damage, but it did get the attention of the goat woman.

"Oh! You're awake! Did you sleep well my child?"

It was a bit strange having the woman call her a child when she was twenty years old, but she didn't complain.

"Uh yeah" she spoke softly as she picked her phone back up. "Are you the one who brought me here?"

"I believe I did. My name is Toriel. I found you laying on a bed of flowers in the Ruins. It's funny really. You are the second human to fall down here in the same night."

The girl's eyes widened hearing that. Frisk had been here?

"T…That other human is my younger sibling! Where are they? Are they okay?"

Toriel placed a comforting hand, or paw, on her shoulder sensing her nerves rising.

"They are doing just fine, but I'm afraid they already left. They had already begun their journey to find their way home."

What? Frisk left without her? Why?

"Come my child. Why don't I offer you a slice of pie and I will explain more to you about the Ruins."

Looking up at the goat woman with white fur the girl felt calm in her presence. The woman looked so kind and gentle. She reminded her of their mother and a tear escaped from her eye as she remembered the dreaded phone call she received last night.

"Oh my!" Toriel exclaimed in slight surprise. "What's the matter my child?"

"E...Everything.." the girl softly whimpered, lowering her head.

Feeling a soft hand gently lift her chin up, the girl's indigo eyes met Toriel's red ones and noticed that her irises were in the shape of a heart. She smiled kindly at her as she wiped her tears away.

"Would you like to talk about it? I'd be happy to listen."

Despite just meeting this woman the girl knew that she could trust her. She was going to miss her when she left to search for her sibling.

"Talking would be nice" she smiled small.

"Splendid! Now before I cut you a slice of pie I must ask. What is your name young one?"

The girl felt a bit rude for not saying it before, but thought now was better than never.

"My name is Echo.."


	2. Calamity

**Hey there Little Souls here is the next chapter of The Souls That Bind Us! I might try and make a schedule for when I update. It depends with all these other projects I'm working on, but I'll see what I can do. Now without further ado here is the next chapter!**

 **XxXxXxX**

It all happened so fast. No one would have been able to predict that the day would end this way. Acting like a ninja nine year old Frisk ducked behind the kitchen table and jumped over a chair. Seeing their goal in sight they ran over to the counter, but frowned seeing that it was too high. That wasn't going to stop them. Opening up the drawers they used them as stairs to climb up. Smiling in victory they reached for a cookie jar only to have a pair of arms pick them up; stopping them from retrieving their goal.

"Gotcha!" a male with brown hair exclaimed, sitting Frisk down on the counter so they were closer to his height. "Hate to break it to ya cookie monster, but the cookies are all gone."

Glancing downward, Frisk pouted, moving to fix the bandage on their knee. The man chuckled and ruffled their hair.

"Tell ya what. Why don't your mom and I run to to store and pick up some ingredients? We can make cookies together when we get back."

Smiling brightly, Frisk nodded excitedly.

"I want chocolate chip!" They signed, speaking with their hands.

"You got it Bucko!"

Jumping off the counter, Frisk ran off to inform their sister just as a woman with medium wavy black hair had entered the room.

"I swear Toby you spoil that child way too much. Your lucky I like chocolate chip as well."

Chuckling, Toby just shrugged and grabbed his keys off the counter.

"We better get going before the cookie monster gets us" he joked, heading into the living room where his two kids were.

Echo sat on the couch, watching something on the television while Frisk sat on the floor in front of her.

"Well be back soon. Keep an eye on Frisk, would ya Echo? Wouldn't wanna lose them."

"No worries dad!" Echo beamed, picking Frisk up off the floor and putting them on her lap. "This ankle bitter is never leaving me!"

Frisk happily nodded in response. Turning to his wife as they headed for the door Toby questioned about what to have for dinner.

"Say Fox, do you think we could pick up a pizza on the way home?"

"Toby we just had pizza last night" his wife reminded.

"What's your point?"

Sighing Fox said goodbye to her kids before dragging her husband out the door. As soon as they were gone Frisk hopped off Echo's lap before quickly tapping her on the arm, confusing her for a moment.

"Tag! You're it!" They excitedly signed before running off.

"Oh it's on!" Echo exclaimed, chasing off after her sibling towards the backyard.

The poor innocent souls were filled with so much joy and laughter. They had no idea that that was the last time they would see their parents. How did it all go so wrong?

* * *

Frisk weren't sure where they were going. They just needed to get away. Far away. They stumbled through the forest, nearly tripping a few times. They constantly wiped at their eyes to whip the tears away that tried to block their vision. Frisk was already mute. They weren't going to add blindness to the list. Stopping to catch their breath Frisk saw that they had reached the mountain. The mountain that their mom had strictly told them to stay away from. There have been stories that other children have fallen inside. It was unknown if they had died or were still simply trapped inside. If the latter was the case then the barrier was keeping them there. They could never go home again.

Contemplating on what to do Frisk froze when they heard a voice. It didn't sound like their sister so who was it? Straining their ears to hear where the voice was coming from Frisk noticed it came from the top of the mountain. Whoever it was seemed to be calling for help. The caring person that they were Frisk decided to save the person. Putting on a determined face Frisk climbed the mountain only to see that no one was up there. Confused Frisk kept looking around to see if they could spot someone. They would have called out for them, but they couldn't. Moving closer to the edge they peered down wondering if the person fell inside. With no one around that seemed to be the case. Frowning sadly Frisk went to turn so they could walk away, but was pushed by some invisible force.

 _"What the...?"_ Frisk thought, quickly looking around.

They were pushed again and this time they fell. Right into the mountain. Silently screaming, Frisk wondered if this was the end. Was it? No it can't be. They wouldn't let it! Finally landing with a loud thud they blacked out for a moment only to wake up a few minutes later and saw that they were laying on golden flowers. The day really wasn't supposed to end this way. They were going to have so much fun. Just mom, dad, Echo, and them. Instead it ended in the worst possible way. Their parent's were gone, they fell in the mountain, and they were all alone. Frisk felt strange. And it wasn't because they just fell through the barrier. It was something else. Something that seemed to be trying to take over their entire being. Frisk tried to shake the feeling off, but it wasn't going away. Sighing they turned their head and that's when they saw it.

A golden flower with a grin on it's face.

* * *

Butterscotch-Cinnamon pie. Why Echo hadn't tried it before was unknown to her. As soon as the sweet flavor had hit her taste buds she had fallen in love with it. It was officially her favorite pie now. She ate every last bite realizing that she was more hungry than she thought.

She had told Toriel everything. From the tragic news to losing her sibling. The goat woman sat quietly as she carefully listened to every word that the dark haired girl said. She had given Echo's hand a gentle squeeze whenever it looked like she was going to breakdown. That was all it took to calm her nerves. The vibe that Toriel gave off was very comforting. She was glad that the woman had opened up to her as well and when it was her turn to listen she learned that Toriel dreamed of becoming a teacher one day. Echo could tell that she was very smart with all the snail facts she shared. She knew that Toriel would be able to conquer her dream when given the chance.

"That's a beautiful locket you have there" Toriel responded, noticing it. "It almost looks familiar.."

"It's my sibling Frisk's" Echo sighed. "I saw that they had lost it when they fell down through the barrier."

"What's inside it?"

"I'm not sure. We've never been able to open it."

"Perhaps it will open when the time is right."

"Maybe.." Echo replied casting her eyes downward.

"Are you alright my child?" Toriel asked in concern.

"I have to find them" she replied. "I'm the only family Frisk has left. I can't just abandon them."

Sighing Toriel slid her glasses off and carefully folded them.

"I wish you didn't have to go. I've enjoyed your company so much. If I let you go I could end up losing two children that I've grown so fond of. But if I keep you here you might not forgive me. There's no real happy solution to this situation, is there?"

Echo felt bad. This poor woman lived all alone and didn't seem to get a lot of company. Which didn't make any sense. This woman was so caring and motherly. Despite being a monster Echo had already grown fond of her as well. She hoped that all monsters were this friendly. She would feel bad for leaving Toriel, but she didn't have a choice. Frisk was her main priority right now. She still wondered why they left without her. If they were found by the same woman they had to have known that she was here. Right?

"I'm sorry" Echo responded apologetically. "Just know that if I didn't have to go on a search party I would have stayed a lot longer."

"It's quite alright my child" Toriel smiled reassuringly as she stood up from her chair. "I understand, but before you go I need you to do something for me."

"Anything!" Echo answered without hesitation.

Oh course she would help Toriel out! She rescued Echo from the Ruins, gave her a bed to sleep in, shared the most amazing pie with her, and listened when she needed someone to talk to. She wouldn't be able to thank Toriel enough.

"I need you to prove yourself to me."

The smile on Toriel's face was now replaced with a serious frown.

"Not all monsters will be trusting of you. Many will try and attack you and you will need to be ready to defend yourself against them. Now please follow me."

Toriel had then led her down some stairs and through a long hallway while explaining some puzzles Echo would have to solve. The warm comfortable feeling that Echo felt before was slowly fading away and was being replaced with an uneasy feeling as if something bad was about to happen. What confused Echo the most was all the dust laying around. There was so much of it for some reason. Why? Finally they had stopped at a large door and Toriel kept her back to her. After a few minutes of uncomfortable silence she turned around to face Echo with a sad smile.

"Forgive me my child.."

Before Echo had a chance to understand what Toriel had meant she began to feel a slight pain emitting from her chest. Her hand gripped where her heart would be and she wondered what the hell was going on. The pressure on her chest increased and it felt as if something was trying to escape. Giving in, Echo pulled her hand away only to see a floating heart burst out. She frowned at it. What was this?

"What you are seeing is your soul" Toriel explained, looking woefully. "It is the very culmination of your being. It will come out whenever you enter a battle."

The way Toriel looked at Echo made her uncomfortable. She let her words sink in and widened her eyes. Whenever she entered a battle? But it came out right now. Did that mean...? To answer her thought Toriel summoned a fire ball before shooting it in her direction. She had told Echo about fire magic during their little chat so it didn't surprise her when she saw it. What did surprise her was the fact that the fire was being aimed right at her. Ducking her head, Echo had barely avoided the blast and widened her eyes at seeing more coming her way. Why was Toriel doing this?

"Toriel stop!" Echo cried, jumping over a fireball.

"Prove yourself my child. Prove to me that you can survive outside the Ruins."

By fighting? Echo was never the strongest person. At least she didn't think so. She continued to dodge, not wanting to fight back. She hissed in pain when one of the flames had managed to hit her right leg. She brushed them off so they wouldn't spread.

"I'm not going to fight you!" Echo yelled.

"If you don't fight then how will you expect to survive?"

How did Toriel expect her to fight back when she didn't have some sort of power or weapon to defend herself with? She was only human. She wasn't as strong as these monsters. Did she have to fight? Wasn't there a different option? Couldn't she mercy them?

Every time Toriel would try and get Echo to attack her she would just spare her every time. Eventually Toriel's attacks seemed to get weaker and she was hardly even trying to hit Echo with her flames anymore. It seemed like she was finally giving in.

"Toriel.. Please stop." Echo pleaded one last time.

Lowering her head, Toriel chuckled sadly.

"Pathetic. I can't even save two innocent souls. You're sibling tried to spare me as well. I can't say the same about the others though. They were just so determined to get through this door. I didn't want them to. I just wanted to protect them. But deep down I knew I couldn't. It wouldn't be right to grow up in a place like this. My expectations... My loneliness... My fear... I had put them all aside.."

 _"Others? There were others here? Did Frisk fight them?"_ Echo wondered.

"And I shall do the same with you my child" Toriel responded, ending the battle and allowing Echo's soul to go back inside her.

Sighing in relief Echo looked up at Toriel only to see that the serious look on her face was back.

"You are about to enter the rest of the underground. You must be careful my child. They... Ashore will try and kill you.. If you want to find your sibling you will have to fight or mercy monsters. What you decide to do it up to you, but remember that it will affect you in the end. It will affect us all."

"I will" Echo replied. "And Toriel..?"

"What is it my child?"

Instead of answering Echo threw her arms around the woman in a warm embrace. Toriel was taken aback a moment, but soon returned the hug.

"Thank you..." Echo whispered.

"There's no need to thank me my child. Now you must get going. You have a long journey ahead if you."

Starting to walk away, Toriel stopped and turned back towards Echo.

"Oh and Echo?"

"Yes Toriel?"

"Beware of the golden prince.."

And with that she was gone. Echo was a bit confused, but decided not to worry about it for now. Turning to face the big doors that led to the rest of the underground, Echo took a deep breath before pushing them open. Her journey had officially begun.


End file.
